The purpose of this study is to compare a dopamine agonist pramipexole with carbidopa-levodopa in the initial treatment of early, symptomatic Parkinson's disease. Parkinson's disease is a very difficult to treat neurodegenerative syndrome and carbidopa-levodopa, a mainstay of treatment, is associated with adverse neurologic reactions. This is a multi-center, randomized, double-blind, parellel, placebo-controlled trial of a total of 300 patients to compare the 2 therapies. The primary outcome measure is the time until the first dopaminergic motor complication, and secondary measures include quality of life and the requirement for supplemental study drug and additional carbidopa-levodopa. Recruitment is completed. Data analysis is not completed in this multi-center clinical trial. The protocol is amended to allow those subjects participating in the accompanying SPECT Imaging study M/2730/0096 to have the final imaging procedure accomplished prior to the study drug being discontinued at the termination of the trial.